. Contributions to embryology. Embryology. RELATIVE WEIGHT AND VOLUME OF COMPONENT PARIS OF FETAL BRAIN. 55 has declined to grams or per cent, which is the lowest mark in the weight-curve for this complex. Of this the olfactory bulb con- tributed per cent, and the paraterminal body, fornLx, and hippocampus, per cent. The mesencephalon likewise reaches its !ov,-est relative level at this stage, weighing Vjut per cent of the total weight of the encephalon. The rhom- bencephalon weighed grams, or per cent, the medulla-pons weighing grams ( per cent) and
. Contributions to embryology. Embryology. RELATIVE WEIGHT AND VOLUME OF COMPONENT PARIS OF FETAL BRAIN. 55 has declined to grams or per cent, which is the lowest mark in the weight-curve for this complex. Of this the olfactory bulb con- tributed per cent, and the paraterminal body, fornLx, and hippocampus, per cent. The mesencephalon likewise reaches its !ov,-est relative level at this stage, weighing Vjut per cent of the total weight of the encephalon. The rhom- bencephalon weighed grams, or per cent, the medulla-pons weighing grams ( per cent) and the cerebellum grams ( per cent). This represents for the former the lowest point in the series, and for the latter a marked gain over preceding figures. In this specimen the total brain constituted per cent of the body-weight, a somewhat greater proportion than is usually reported. Jackson (1909) gives per cent and Vierordt (1893) per cent. ^Globus I palMus. Hypothal, Fig. 10.—Meaial view of right half of telencephalon of embryo shown in fig. 9. X 2. FiQ. 11.—Mesial view of the Bubdi\'ided archipallium of embryo shown in figs. 9 and 10. X 2. Fig. 12.—Drawing of a hemisection of brain shown in figa. 9,10, and 11, with subdivisions of basal ganglia outlined. (Section 6, slide ;) X 2. BRAIN VOLUME AT DIFFERENT STAGES. Since we have the volume of the models of the brain and its separate parts for the different stages of development, it is possible to roughlj^ calculate the actual volume by dividing the model volume by the cube of the magnification used for the reconstruction. It must be borne in mind, however, that since we are dealing with brains that have been embedded in paraffine or eel- t^ble of brain at different loidin, the models represent the embedded brain and one must take into account a considerable shrinkage of the tissues. The shrinkage of a given brain is more or less uniform throughout and therefore, in itself, doe
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